Evoluzione tettonica e geomorfologica della Piana del Sele (Campania, Appennino Meridionale)

Tectonic and geomorphological evoltion of the Sele Plain (Campania, Southern Apennine)

Abstract

Sele River alluvial coastal plain, occupying the innermost portion of a structural depression (the Gulf of Salerno Graben), cuts almost transversally the Tyrrhenian slope of the Apennine chain and attains a total maximum ithrow of about 3000 m. While the western half of this graben (i.e. the present day submerged portion into the Tyrrhenina Sea) remained always submerged, the eastern portion has experienced a more complex tectonic history: after a Tortonian-Messinian phase of marine deposition it entered a period of emersion and erosion which went on until the Middle Pliocene at least. During that span of time a mature landscape of low relief amplitude developed on the western side of the chain. Probably durin the Upper Pliocene a period of intense block – faulting broke up said landscape, lifted fragments of it several hundred meters above the sea-level and caused a new phase of subsidence of the inner portion of Salerno Graben. Depending on the increased relief of its interland, the depression experienced a huge and coarse clastic deposition, which gave rise to the thick «Conglomerati di Eboli» formation. Possibly during the Possibly during the Middle Pleistocene and not later than 0,4 ma. b.p. the area was affected by two tectonic phases. As a result, the Eboli formation was in blocks up to 400 m a.s.l. while the Picentini Mts., lying behind, rised of a double amount. The subsequent renewal of erosion caused new generations of alluvial deposits to accumulate downslope of the raises sectors, where the Sele Plain started then to grow. The discovery and dating of some distinct ancient beach features allowed us to reconstruct that the coastline was 7 km inland of present one 0.13 m.a. b.p., some 3 km inland 0,10 m.a. b. p. and almost 1 Km inland during the Holocene maximum high-stand. The present elevation of the two Tyrrhenian beaches (25 and 13 m. a.s.l. respectively) leads us to infer that moderate uplift both during and after the last interglacial. On the contrary the elevationt og the beach sands underlying the Holocene dune bars (1,5-2 m a.s.l) seems to denote a substantial tectonic stability of the plain during the last millennia.